Because of environmental concerns there is a great demand to develop a process for producing high octane isoparaffins for blending in the gasoline pool. Isoparaffins are conventionally produced by isomerization. In isomerization, as conventionally operated, low molecular weight C.sub.4 to C.sub.6 n-paraffins are converted to isoparaffins in the presence of an acidic catalyst such as aluminum chloride or an acidic zeolite, as described in G.B. Patent No. 1,210,335. Isomerization processes for pentane and hexane which operate in the presence of hydrogen have also been proposed using acidic catalysts. See Maxwell, I.E., "Zeolite Catalysis in Hydroprocessing Technology," Catalysis Today. 1, 385-413 (1987) and Meyers, R.A., Handbook of Petroleum Refining Processes, 5-3 to 5-24 (1986).
High octane isoparaffins are also produced by acid catalyzed alkylation of an isoparaffin with an olefin. Industrial alkylation processes have historically used hydrofluoric or sulfuric acid catalysts. For a general discussion of sulfuric acid alkylation, see the series of three articles by L.F. Albright et al., "Alkylation of Isobutane with C.sub.4 Olefins," Ind. Eng. Chem. Res., 27, 381-39, (1988). For a survey of hydrofluoric acid catalyzed alkylation, see Handbook of Petroleum Refining Processes, 23-28 (1986).
The process of the present invention avoids several disadvantages over prior art processes as the process of the present invention is not limited to C.sub.7 --feeds or the use of a corrosive acid catalyst.